1. Field of the Invention
The present invention relates to a wide-angle lens system for examining an object at a finite distance with high definition, and for use in processing an object image.
2. Description of the Prior Art
In the prior art, wide-angle lens systems for surveillance cameras have been disclosed in, e.g., Japanese Unexamined Patent Publication (hereinafter, JUPP) No. 2001-208967, JUPP No.H09-127413, JUPP No.H07-63986, and JUPP No.H04-11209.
However, in the wide-angle lens system disclosed in each of these publications, distortion is noticeable, and such a wide-angle lens system cannot be used for image processing in which the optical ability with a higher definition is required. Furthermore, the overall length of the wide-angle lens system disclosed in these publications is relatively long compared to the focal length.
On the other hand, there has been a wide-angle lens system which is designed for photographing purpose. This type of wide-angle lens system is disclosed in, e.g., Japanese Unexamined Patent Publication No. H05-188294; however, the amount of peripheral illumination is smaller. If an attempt is made to increase the amount of peripheral illumination, coma of higher order occurs. Consequently, the optical performance with higher definition cannot be attained, and hence such a wide-angle lens system cannot be used for image processing.